Device for discoupling relays



NOV-v 1969 CARL-GUSTAVS. JOHANSSON 3,

DEVICE FOR DISCOUPLING RELAYS Filed Dec. 8, 1966 FIG.2

CARL-GUSTAV SIMON JOHANSSON 'INVENTOR ATTORNEYS United States Patent "ice 3,480,839 DEVICE FOR DISCOUPLING RELAYS Carl-Gustav Simon Johansson, Molndal, Sweden, assignor, by mesne assignments, to Aktiebolaget Gylling & Co., Stockholm, Sweden Filed Dec. 8, 1966, Ser. No. 600,236 Claims priority, application Sweden, July 1, 1966, 9,002/ 66 Int. Cl. H01h 47/18 US. Cl. 317-142 2 Claims ABSTRACT OF THE DISCLOSURE Means for disconnecting a relay of the self-holding type wherein a current circuit has the relay connected therein, A transistor is connected in parallel with the relay and a resistance controlled by temperature is connected in series with the relay. A resistance controlling the current through the transistor is connected between the base and the collector of the transistor and a switch is connected between the transistor base and one pole of a source of current with a condenser connected in parallel with the switch. A second transistor may be connected between the base and the collector of the first-mentioned transistor with the base of said second transistor connected to the junction point between the resistance controlling the current andthe condenser.

When it is desired to operate a relay by means of a transistor, the latter is usually coupled in series with the coil of the relay. It is then possible to control the coupling and the discouplin-g of the relay by means of supplying different voltages to the base of the transistor. This coupling necessitates the whole of the operation current of the relay to pass through the transistor whereas on the one hand the voltage drop between the collector and the emitter of the transistor reduces the sensibility of the relay and on the other hand there is caused a continuous development of effect in the transistor as long as the relay is connected.

The purpose of the present invention is to eliminate these drawbacks. The main feature of the invention is to be seen therein that the transistor is coupled in parallel with the relay which is self-holding, that a resistance, controlled by the temperature, e.g. a special lamp, is coupled in series with the relay, that a resistance controlling the current through the transistor is connected between the base and the collector of the transistor and that a switch is connected between the base and one pole (the positive pole) of the current source.

An advantage of this device is to be seen therein that the relay retains its sensibility and that no continuous effect is developed in the transistor when the relay is connected.

Further features and advantages of the present invention will be obvious from the following description with reference had to the accompanying drawing. In the drawmg:

FIGS. 1 and 2 show two difierent coupling diagrams according to the invention.

According to FIG. 1 there is in series with a relay 1 coupled a lamp 2 with a resistance wire which with increasing temperature increases its resistance value and which is connected between the positive terminal and negative terminal of the voltage source. The relay 1 is provided with a self-holding contact 3. A transistor 4 is coupled in parallel with the relay 1. A resistance 7 controlling the current through the transistor is connected between the base 5 and the collector 6 of the transistor 4. The emitter 8 of the transistor 4 is connected to the 3,480,839 Patented Nov. 25, 1969 junction point 9 between the relay 1 and the lamp 2. At switch 10 is connected between the resistance 7 and the positive pole of the voltage source.

The switch 10 is supposed to be initially closed. When the contact 3 is closed, current flows from the positive pole through the lamp 2 and the relay 1 and passes then through the contact 3 to the negative pole. For the reason that the switch 10 is closed, no current will pass through the transistor 4. The reason for this is that when the lamp 2 which has a certain resistance, causes a voltage drop, the potential at the emitter 8 will be somewhat lower than the potential at the base 5, where there occurs the full voltage. The lamp 2 is to be chosen in such a way that the voltage drop over the same will at maximum be 0.3 volt. When the switch 10 is opened, a current will pass from the emitter 8 of the transistor via its base 5 and through the resistance 7 to the negative terminal. The transistor 4 is then opened whereby a higher current is caused to pass through the lamp 2. The resistance wire in the lamp will thereby be further heated which causes an increase in its resistance value, and the voltage drop over the relay 1 is reduced to such an extent that the relay will fall.

Beside the advantage mentioned this coupling also gives that advantage that in case the lamp and the relay are dimensioned for a certain voltage, the induced voltage may e.g. be doubled without causing any detrimental increase in the current through the relay which is due to the fact that the lamp 2 functions as a limiting device for the current. In case the battery voltage as mentioned should be e.g. 6 volts and the voltage drop over the lamp is 0.3 volt, there occurs a voltage drop of 5.7 volts over the relay 1. On the other hand if a battery of 12 volts is coupled to the device there is obtained a voltage drop of about 4 volts over the lamp which is heated to a higher temperature and thereupon the voltage drop over the relay will be about 8 volts. At an increase of the battery voltage with the increase in the voltage over the relay 1 will be only 85.7=2.3 volts i.e. only about 40%. Such a rather modest voltage increase can be sustained by the relay.

The very eminent advantages of the device are the following ones:

(1) The lamp does not remarkably influence the sensibility of the relay.

(2) The lamp compensates the voltage alterations.

(3) No loss effect occurs in the transistor 4 when the relay 1 is connected for the reason that the whole of the current passes through the relay.

(4) The transistor has a short connection time.

In FIG. 2 there is shown an application of the coupling for obtaining a retarded releasing of a relay with a selfholding contact.

50 as to obtain long times of retardment a further transistor 11 has been connected in series with the transistor 4. A condenser 12 has further been coupled in series with the switch 10. A spring-loaded contact 13 has been connected between the positive pole of the current source and the lamp 2.

For bringing the relay 1 to attract, one pushes on the spring-loaded contact 13 whereby current flows from the positive pole of the voltage source via the lamp 2 and the relay 1 to the negative terminal. When the switch 10 is closed full positive potential is applied to the base 14 of the transistor but a lower potential is applied to the emitter 15 of the transistor 4 due to the voltage drop over the lamp 2. The transistors 4 and 11 thus are shut. When the switch 10 is opened, the condenser will slowly be charged over the resistance 7 whereas the charging time is depending directly on the values of the resistance 7 and the condenser 12. Thereby the potential at the base 14 of the transistor will be slowly reduced and a current will pass via the lamp 2, the transistor 4 and the transistor 11 to the negative pole. As the potential of the base 14 drops, the current will increase through the lamp 2 and when it has reached a value sufliciently high, the voltage drop over the relay 1 will, due to the heating of the lamp, be reduced to such an extent that the relay falls and the current circuit is cut 011? over the contact 3.

The invention has been described in the aforegoing for purposes of illustration only and is not intended to be limited by this description or otherwise except as defined in the appended claims. Thus, the couplings may be varied in many different ways without departure from the inventive idea. The transistor 11 may be dispensed with. It might also be advisable to couple further transistors in series with the transistors 4 and 11.

What I claim is:

1. Means for disconnection of a relay of the selfholding type comprising a source of current, a current circuit having said relay connected therein, a transistor in said circuit connected in parallel with said relay, a resistance controlled by temperature connected in series with said relay, a resistance controlling the current References Cited UNITED STATES PATENTS 2,340,502 2/1944 Baker.

3,118,091 1/1964 De Sautels 317148.5 3,360,693 12/1967 Fickweiler 3 17-148.5 3,376,429 4/1968 Atkins 317--148.5

LEE T. HIX, Primary Examiner D. J. HARNISH, Assistant Examiner US. Cl. X.R. 317-1485, 154 

